Electric furnace.



PATENTED SEPT. 6, 1904.

M. R. GONLEY. ELECTRIC FURNACE.

APPLICATION FILED 00T.1. 1902. RENEWED JAN. 27, 1904.

N0 MODEL.

' ATTORNEY,

Patented September 6, 1904.

UNITED STATES PATENT OEEIcE.

MICHAEL R. CONLEY, OF NEXV YORK, N. Y., ASSIGNOR TO ELECTRIC FURNACE COMPANY, OF NElV N EW' YORK.

YORK, N; Y., A CORPORATION OF ELECTRIC FURNACE.

SPECIFICATION forming part of Letters Patent No. 769,250, dated September 6, 1904.

Application filed October 1, 1902. Renewed January 27, 1904. Serial No. 190,900.

To alt whom. it may concern:

Be it known that I, MIoHAEL R. OoNLEY, of the borough of Brooklyn, city of New York, county of Kings, and State of New York, have invented certain new and useful Improvements in Electric Furnaces, of which the followingis a full, clear, and exact description.

My invention relates to improvements in electric furnaces in which the heat is produced by the passage of an electric current through a portion of the said furnace, consisting of a composition which resists the passage of the said current in the manner set out in United States Letters Patent N 0. 558,357 to me, dated April 14:, 1896; and the object of my invention is to produce a simple form of incandescent electric furnace in which the distribution of the electric current, and consequently of the heat, shall be practically uniform through all the heating portion of the said furnace,

but may also be capable of variation in case it becomes desirable to increase or decrease the heat in one particular part of the said heating portion, and, further, to produce an electric furnace in which the heat may be prevented from being radiated away and may be confined to the heated portion of the said furnace in such manner as to result in a high degree of efliciency. and in preventing any overheating of the conductors which lead the electric current to the furnace or of any adjoining pieces of apparatus.

Reference is to be had to the accompanying drawings, forming part of this specification, in which similar letters of reference apply to similar parts throughout the several views.

Figure l is a vertical cross-section of the furnace, showing the conducting-arms in elevation. Fig. 2 is a horizontal section along the line 2 2 of Fig. 1. Fig. 3 shows amodification of Fig. l, the brickwork and packing being omitted for the sake of simplicity and the electrical connections being indicated diagrammatically.

A is a receptacle for the purpose of containing the substance to be acted upon and may be approximately in the form of an or dinary crucible, as shown in Figs. 1 and 2, in

(N 0 model.)

which case it may be referred to as a crucible, or it may be in the form of a cylinder, as shown in Fig. 3, in which case the cylinder rests upon a block X of some non-coir ducting substance, as fire-brick, which forms a bottom to the said receptacle. A removable cover B may also be provided.

The receptacle A is made of a composition which resists the passage of a current of electricity, for which purposeI find that earthenware consisting of graphite, silica, and fircclay, asin an ordinary graphite crucible, is well adapted. The receptacle A is made under heavy pressure in a mold and is not spun or turned, as is the ordinary graphite crucible, because this latter method of manufacture leaves minute cavities in the finished article which, although harmless in the ordinary furnace-crucible, tend to produce arcs upon the passage of an electric current and ultimately to form large holes, which would render the receptacle useless. It is understood, however, that while I have described a receptacle consisting of fire-clay, silica, and graphite I do not limit myself to this or any particular composition. The receptacle A is provided with an insulating-lining a, which prevents the electric current from being shortcircuited through the metal or other contents of the receptacle A. This insulatinglining consists of a composition which becomes plastic when subjected to a high degree of heat, and thereby tends to close up any cracks which may exist in the receptacle.

The receptacle A, which is approximately uniform in thickness, as shown in Fig. 2, is provided with a horizontal extension or wing c c on each side reaching from the top to the bottom of the said receptacle A and approximately uniform in cross-section, and into these extensions 0 c the tenons (Z of the carbon arms O'O are mortised. The extensions c c perform a double function. First,

they serve as a suitable support for the arms C O, and, secondly, they form conductors which tend to distribute the current vertically and to widen its path, and thereby to prevent local overheating and the formation of cracks, which would be the result if the current were allowed to flow in a narrow band or Zone, as it would do were the extensions 0 c omitted. For the purpose of obtaining a tight joint a cement consisting of graphite and a hydrocarbon, as molasses, is used, and on the application of heat the hydrocarbon is carbonized and the arms 0 c and the receptacle A become an absolutely unbroken path for the electric current. It is understood, however, that I do not limit myself to any particular composition or cement except such as will accomplish this result.

To the outer ends of the arms C C the metallic plates D D- are bolted, and to these plates are connected the leads E E, which conduct the electric current from the generator G, as shown in Fig. 3, which figure shows the leads connected with the main F, and also four separate arms U C C C, two on each side of the receptacle A, each arm being supplied with 'a separate lead and also with a switch S S S S, by means of which it becomes possible to vary the distribution of the current by opening and closing the various switches. IVhile only four such arms are shown, it will be evident that any number may he used, depending upon the shape and size of the receptacle A, and it is understood that I do not limit myself to any particular number.

A rheostat may be used in circuit with the furnace for the purpose of controlling the flow of the electric current through the furnace; but it is obvious that any controlling device to efifect this end may be substituted, and I find that the diagrammatic arrangement illustrated in Fig. 3 is well adapted to practical use. In this figure, T indicates a stepdown transformer in an alternating-current circuit. Z is the secondary circuit, which is in series with the furnace, and P is the primary, which is in series with the generator G and the variable choke-coil R. It will be obvious that it is vastly easier to control the secondary current indirectly by means of controlling the primary current with this arrangement or a similar one. than to control the secondary current directly, as the secondary current may sometimes amount to one thousand amp'eres or perhaps twenty times as much as the primary current, and consequently would require very large, costly, and unwieldy apparatus, the change of resistance as the furnace heats up being considerable. With several of these arrangements it is also possible to use a single generator to operate an equal number of furnaces, whereas a direct current if used would require a very large and wasteful rheostat for each furnace on a separate generator provided with a field-rheostat. Insteadof the variable choke-coil R the transformer T may be provided with a movable core, or any other means may be used to vary its output.

The receptacle A and the arms C C are maintained in proper relation to each other by means of the brickwork H, (not shown in Fig. 3,) and around the receptacle A is packed a non-conducting substanceK for the purpose of supporting the walls of the receptacle A and also to prevent radiation of the heat, for which purpose I find dry fire-clay well adapted. I have also found by experiment that by having this packing of fire-clay in powdered or granulated form it serves not only to prevent radiation, but in case an arc starts in the furnace-wall the broken non-conductor falls into the place eaten out by the arc and sticks close to the furnace, so as to prevent the arcing. I have found, further, that if the material of the furnace has only sufiicient conducting matter to cause the current to start through it when the furnace becomes hot the current will continue to traverse and heat it even though the conducting matter is burned out.

While I have shown the receptacle A of approximately circular cross-section, it is understood that I do not limit myself to this exact shape, but may use a receptacle rectangular in cross-section or otherwise. It is also understood that only a portion of the receptacle A need be of resisting material, while the rest may consist of a non-conducting substance, and the heating portion may be in form a slab or bar or other convenient shape without departing from the spirit of the invention.

Having thus described my invention, what I claim as new, and desire to'secure by Letters Patent, is

1. In an electric furnace, the combination with the receptacle having its walls formed of a resisting medium adapted to become incandescent on the passage of an electric current through it, of a plural series of arms of greater electrical conductivity than the said furnace, the several series 'being arranged in different planes to the end that the current may be passed through one or more series as desired to vary the electrical distribution in the furnace.

2. In an electric furnace, the combination with the resisting medium adapted to become incandescent on the passage of an electric current through it, said medium forming a receptacle to receive a charge, of a plural series of arms connected to the said receptacle, the arms being of greater electrical conductivity than the said resisting medium and the series of arms being arranged in different planes, each arm being provided with a switch to the end that the electrical distribution through the furnace can be controlled.

3. In an electric furnace, the combination with the resisting medium adapted to become incandescent on the passage of an electric current through it,'said medium forming a receptacle to receive a charge, of a plural series of connections connecting withthe furnace in different planes, each connection being pro- ITO vided with a switch to the end that the electrical distribution through the furnace can be controlled.

4. An electric furnace comprising a receptacle formed of resisting material adapted to grow incandescent on the passage of an electric current through it, integral extensions on opposed portions of the furnace, and a series of connections connecting With the said extensions in different planes to the end that the electrical distribution through the furnace may be controlled.

5. An electric furnace of the kind described, comprising a body portion of resisting material adapted to grow incandescent on the pasto this specification in the presence of tWo sub- 25 scribing Witnesses.

MICHAEL R. OONLEY. lVitnesses:

WM. H. OAMFIELD, J. G. DUNBAR. 

